Instyle LED Lighting Specialists UK
This official sponsor may provide discounts for members

Discuss 10.8kW shower cable size in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

D

DSpark1

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:  American Electrical Advice Forum

Hi,

I'm installing a 10.8 kw shower and looking at other forums everyone is saying 10mm is OK however i can't see how.

10800W/230V=47A

breaker size 50A

the only way it can be a 10mm is if its clipped direct with no insulation as it can take 64A however if it is any other reference then the rating is less than 50A.

so how is 10mm enough to carry the load?

what have i missed?
 
Last edited by a moderator:
uHeat Banner - Forum Discount Available
This official sponsor may provide discounts for members

snowhead

-
Mentor
Don't the Regs over rule what people on forums say?

Using your first method, it complies.
Otherwise it doesn't.
So half the people are correct, or is that all of the people are half correct?
 
D

DSpark1

  • Thread Starter Thread Starter
  • #4
The purpose of the breaker is to protect the cable from overloading or burning due to overload
I think you just helped me answer the question as it can't overload as a shower is a fixed equipment. Under fault it will trip anyway. However 10mm is boarderline as the current carrying capacity of it is 45-47 amp with ref method 100 and 102 which are the most common for domestic
 
O

Octopus

  • Thread Starter Thread Starter
  • #5
Bottom line is that you are the one signing off the new circuit/notification so you need to decide.

Maybe a bit of 16mm is the way to go......

Call your scheme's technical helpline and see what they say.

More information required me thinks
 

Risteard

-
Arms
Esteemed
However 10mm is boarderline as the current carrying capacity of it is 45-47 amp with ref method 100 and 102 which are the most common for domestic
I agree with what was stated on the IET Forum to you, which is that Clipped Direct (C) is by far and away the most common reference method in a domestic installation. Also, as said, the shower is a fixed load which cannot overload and so the protective device need only provide fault protection.
 

darkwood

Mod
Mentor
Arms
Esteemed
The mcb provides both overload protection for the cable and fault protection for the circuit, to suggest that just because the load is fixed and cant go any higher is wholely irresponsible, what if you have a insulation fault either in the cable L/N or shower(partial element short reducing its resistance) this can raise the current without showing a fault. If i was installing any cable through a loft i would fit a trunking 2/2 where it passes through the insulation and have the cable run above any possible insulation level, and with goverment policies to have all homes insulated at some point i would install the trunking whether insulation there or not, if the cable calcs dont comply then dont cut corners either upsize the cable or choose a different route or method.
 
Last edited:

Risteard

-
Arms
Esteemed
The mcb provides both overload protection for the cable and fault protection for the circuit, to suggest that just because the load is fixed and cant go any higher is wholely irresponsible
How so? The Wiring Regulations specifically permit the omission of overload protection where supplying a fixed load which cannot overload.

darkwood said:
what if you have a insulation fault
Hence why you must ensure that it provides adequate fault protection as I stated.
 

darkwood

Mod
Mentor
Arms
Esteemed
A fixed load that cannot overload is like a motor with overload protection or a fixed device with its own fusing, this case the current can't exceed the overload setting or device fuse, you may install a cable of less than 3m where the protective device upstream is higher as long as the device downstream protects the cable from overload.
Now this is how i was taught and if things have changed with the plight of rcd's on everything il stand corrected as extra protection has been afforded.
 
I remember at college I worked out an 8.5kw shower with all the factors and cable run come to a 16mm,
It was a question that was designed to see how working out was acheived by having above normal problems to overcome but the main question was how were we to get a 16mm into the terminal block.
 
10mm is good enough surely not come across a shower wired in 16mm myself would you physically be able to terminate a 16mm in to a shower
 

darkwood

Mod
Mentor
Arms
Esteemed
Example of reg 433.3.1 (ii).. would be fitting a 2way board with 2 x 16a mcb's you could effectively feed board of an Henley block in 6mm tails regardless of how large the fuse up-stream was because it cant draw long term a load exceeding the value of both mcb's.
 
D

Deleted member 9648

  • Thread Starter Thread Starter
  • #13
433.1.1 (ii) states that the rated current of the overload device must not exceed the current carrying capacity of the circuit cable...in which case a 50a mcb on a 47a rated cable will not comply.
But...433.3.1 states overload protection may be ommitted where the characteristics of a load means an overload is unlikely,provided the device provides fault protection.
IMO a fixed load like a shower is unlikely to overload.
 
433.1.1 (ii) states that the rated current of the overload device must not exceed the current carrying capacity of the circuit cable...in which case a 50a mcb on a 47a rated cable will not comply.
But...433.3.1 states overload protection may be ommitted where the characteristics of a load means an overload is unlikely,provided the device provides fault protection.
IMO a fixed load like a shower is unlikely to overload.
Agreed.
 

darkwood

Mod
Mentor
Arms
Esteemed
And as i said il stand corrected, of which i do... having thoughts regarding a shower it does have thermal fusing within too as a back-up but yes as long as cable does not underate mcb then il also agree, my prehistoric teachings only included loads with their own protection for overloads but regs change so much im bound to miss the odd change.... viva la 15th edition ;)
 
CK Tools :) The professionals choice when it comes to Electrical Tools
This official sponsor may provide discounts for members

Reply to 10.8kW shower cable size in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

Wetroom Store - Network Wetroom Suppliers
This official sponsor may provide discounts for members
Test Meter - Forum Sponsors since 2007!
This official sponsor may provide discounts for members
Top Bottom